Radio Frequency (RF) switches are widely used in mobile phones and other portable communication devices. They are used to switch communication between transmit and receive modes as well as for switching between ranges of frequencies in multi mode/band radios. They also may be integrated into tunable filters, transceivers, phase shifters and smart antennas. The level of insertion loss of a RF switch directly affects the range and battery life of any device using the switch, for example, cell phones, wireless local area networks, and broadband wireless access devices.
Traditional solid-state RF switches, such as GaAs FETS and PIN diodes that are controlled electronically, often suffer from high insertion loss. Micro-Electro-Mechanical System (MEMS) based RF switches may offer operation at a lower insertion loss.
A desirable feature in a MEMS switch is a high contact force, e.g., larger than 200 μN, in order to achieve low contact resistance, and thus the ability to pass more current through the switch for higher power handling capability. Electrostatic actuation is widely used in applications that require a high switching speed, e.g., on the order of 10 μs or less. Conventional switches generally require an actuation voltage of more than 60 Volts (V) in order to obtain a contact force on the order of 200 μN. Trying to achieve such high contact forces in a conventional switch at lower actuation voltages, e.g., on the order of 20V, would result in high power consumption and may damage a contact point of the switch, thereby shortening the effective lifetime of the switch.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.